Waterborne inputs of heavy metals
In 2004 the reported waterborne (including coastal areas) mercury load entering the Baltic Sea amounted to 2.5 tonnes, the lead load to 120 tonnes, and the cadmium load to 6.2 tonnes. During the period 1994-2004 riverine heavy metal loads (notably Cd and Pb) seem to have decreased for most of Contracting Parties. However, incomplete data from some countries makes it difficult to draw conclusions concerning the total heavy metal load into the Baltic Sea.
Results and assessment
Relevance of the indicator for describing developments in the environment
High concentrations of heavy metals in biota of the Baltic Sea is mainly caused by loading from the land-based sources. In 2004 about 50 % of cadmium and lead, and 40 % of mercury entered the Baltic Sea via rivers or as direct waterborne discharges. The rest originates from atmospheric deposition.
Policy relevance and policy references
Excessive heavy metal concentrations may pose a health risk to the marine biota and to humans. In the Baltic Sea high concentrations of mercury, cadmium and lead have been measured in fish, in birds' eggs and in the seal tissue, for instance. Measured concentrations of heavy metals have typically been as much as an order of magnitude higher than concentrations in the North Sea. The main reason behind these high concentrations in the Baltic Sea is intense industrial activity, high populations in the catchment area, and above all the long renewal time of the seawater. Quantified annual information on the waterborne inputs of heavy metals is needed for evaluation of long-term changes of heavy metal concentrations in biota and the state of marine environment.
Due to the incomplete data on heavy metals, a good quantitative picture of the loads entering the Baltic Sea cannot be given. Shortcomings in national monitoring programs and the lack of proper laboratory equipment meant that heavy metal figures were not obtained in many cases, or the loads reported are not fully reliable (no harmonized detection limits in all HELCOM countries). Also different calculation methods have been used in the countries if the measured concentrations have been below the detection limit. The data sets of unmonitored rivers and coastal areas are even more incomplete.
The riverine heavy metal loads also vary to some extent with runoff from year to year, but not to the extent as nutrient loads due to their origin (industry, waste water treatment plants). To be able to evaluate the reductions of heavy metal load from land-based sources comparable, reliable and extensive long-term data (since early '80s) should be available.
Figure 1. Total waterborne inputs of lead in t/year to the Baltic Sea during 2004 for the 9 HELCOM countries.
Figure 2. Total waterborne inputs of cadmium in t/year to the Baltic Sea during 2004 for the 9 HELCOM countries.
Figure 3. Total waterborne inputs of mercury in t/year to the Baltic Sea during 2004 for the 9 HELCOM countries.
Figure 4. Time series of waterborne loads of lead in t/year to the Baltic Sea and the river, coastal and direct point source flow in m3/s for the period of 1994-2004 of the 9 countries. (Note variable scales in the graphs)
Figure 5. Time series of waterborne loads of cadmium in t/year to the Baltic Sea and the river, coastal and direct point source flow in m3/s for the period of 1994-2004 of the 9 countries. (Note variable scales in the graphs)
Figure 6. Time series of waterborne loads of mercury in t/year to the Baltic Sea and the river, coastal and direct point source flow in m3/s for the period of 1994-2004 of the 9 countries. (Note variable scales in the graphs)
Table 1. Riverine, coastal and point source flow to the Baltic Sea of the 9 HELCOM countries in 1994-2004, m3/s.
Table 2. Riverine, coastal and direct point and diffuse source inputs of lead of the 9 HELCOM countries in 1994-2004 as t/year.
Table 3. Riverine, coastal and direct point and diffuse source inputs of cadmium of the 9 HELCOM countries in 1994-2004 as t/year.
Table 4. Riverine, coastal and direct point and diffuse source inputs of mercury of the 9 HELCOM countries in 1994-2004 as t/year.
HELCOM PLC data base
Meta dataTechnical Information:
1) Data have been collected by the Contracting Parties of HELCOM and submitted to the Pollution Load Compilation database (PLC database). The data base is located in Finnish Environment Institute (SYKE).
2) Description of data: The data are based on annual average concentrations (mg/l) of nutrients and their fractions (Ptotal, PO4-P, Ntotal, NH4-N, NO2-N, NO3-N and NO2,3-N), concentrations of heavy metals (Cd, Pb and Hq) and mean flows (m³/s). The contracting parties have calculated the annual loads (t/a) of monitored and unmonitored rivers, coastal areas and direct point sources. From 2003 on also loads on direct diffuse sources have been collected. All these data have been pooled together as total loads to the Baltic Sea by country.
Monitored river loads and most of the point source data are based on measurements, and unmonitored river catchment, coastal area loads and direct diffuse loads on estimates, respectively.
3) Spatial coverage: drainage of the Baltic Sea of 9 riparian countries; Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia and Sweden, including the drainages of the Baltic Sea in Belarus, Czech Republic, Norway, Slovakia and Ukraine.
4) Transboundary rivers: To avoid double data reporting of the transboundary rivers, their loads have been included in as follows:
River Tornio (Finland)/Torne älv (Sweden): in the Swedish data
River Narva (Russia and Estonia): in the Estonian data
River Oder (Poland): in the Polish data
5) Temporal coverage: Nutrients 1994-2004 and Harmful substancies 1994-2004Data Quality:
1) Methodology and frequency: variable, basically as agreed on the PLC-4 guidelines for monitored rivers daily flow and concentration regression or monthly flow and concentrations, and for unmonitored areas loads based on the surface area comparison with a similar monitored area.
2) Heterogeneous data in space and time and may cause some variation between years. Due to robust analysing methods in some countries reported loads might be too high.
Only the missing data of all sources, i.e. monitored rivers, coastal area and direct point and diffuse sources, have been listed below. Therefore, more data may be partially missing.
Flow: No data of 2004 have been submitted from Russia and Latvia.
Nitrogen: No data of 2004 have been submitted from Russia and Latvia.
Phosphorus: No data of 2004 have been submitted from Russia and Latvia.
Lead: No data of 1994, 1996-1999 and 2002-2003 from Denmark, no data of 1996-1999 and 2001-2004 from Estonia, and no data of 2004 from Latvia and Russia.
Cadmium: No data of 1994, 1996-1999 from Denmark, no data of 1995-1999 and 2001-2004 from Estonia, no data from Russia 2002-2004, no data from Lithuania 2003-2004 and no data of 2004 from Latvia.
Mercury: No data on mercury from Latvia, no data of 1994, 1996-1999 from Denmark, no data of 1995-1999 and 2001-2004 from Estonia, no data from Lithuania of 1994-1998 and 2002, and no data from Russia 2004.
Missing data have been listed in table 5.
|DENMARK||1994, 1996-1999, 2002-2003||1994, 1996-1999||1994, 1996-1999|
|ESTONIA||1996-1999, 2001-2003||1995-1999, 2001-2004||1995-1999, 2001-2004|
For reference purposes, please cite this indicator fact sheet as follows:
[Author’s name(s)], [Year]. [Indicator Fact Sheet title]. HELCOM Indicator Fact Sheets 2005. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.
Last updated 25 Nov 2005.